Process for producing phenol from cyclohexanol and cyclohexanone



Patented July 28, 1942 UNITE-o s TArE S PRocEss FOR PRODUCING PHEN OL FROM OYGLOHEXANOL AND CYCLOHEXANONE Edward P. Bel-d cree Edmund Field, Wilmington, Del., assignors to Eel. du Pont de Nemom's &om'pany,-Wilmington, Del.) a corporation of Delaware e Drawing.

14 Claims.

This invention relates to catalytic dehydro application December Serial No. 311,120.

genation processes and more particularly'to cat alytic dehydrogenation of cyclohexanol and cyclohexanone to phenol.

It has been intimated in the prior art that cyclohexanol, may bedehydrogenated to phenol. Thus Sabatier and Senderens (Comptes rendu 137, 1026 (1903)) showed passage of a mixture of cyclohexanol and cyclohexanone over reduced copper at 300 (in the absenceof hydrogen), and stated that phenol was produced during. the

1 process but decomposed to give traces of higher pyrogenous products. Skita and Ritter (Berichte 44, 668- (1911)).state that when cycle hexanone is hydrogenated over nickel at 230? C.

% of phenol is collected along withthe cyclohexanol. In Reid's translation of Sabatier: Catalysis in Organic Chemistry (second printing) genate cyclohexanolto phenol over a reduced copper oxide catalyst 'at 350,4.3% of the alcohol was converted to phenol and 9% was dehyweight, and inasmuch asfthe phenol-cyclohexanol binary at 760 mm. contains 12% cyclohexanol and 88% phenol (the'phenol content of this. binary drops as pressure is decreased). a rela-U tively small amount of cyclohexanone' or cyclohexanol. unreacted wm absorb, or segregatein the form of a binary, a large quantity of phenol."

Accordingly with "low conversions of the order 01 at'the maximum it isn'ot feasible to separate the phenol from the unreacted products by] the "usual, distillation technique. That isto say, the conversion 'to phenol should be, greater.

than 71% before a greater quantity of phenol will be formed than .is required for satisfaction of its binary mixture composition with cyclohexanone. A similarsituation rises with respect to the cyclohexanol binary. Ordinarily, however, thecyclohexanol is present in only small quantities and the recoveryproblem is ahnost exclusivee 1y that for recovery 01 the ketone and phenol.. 1 A study of the equilibrium involved in the conversion of cyclohexanol"and cyciohexanone to phenol has shown that relatively'high tempera tures as, for example, temperatures. above,,350 are req'uiredi! substaritially high' conversions are to be obtained. Our studies show,,howeve :r, that drated while conversion to cyclohexanone was 75%. We obtained somewhat similar results when the catalyst was reduced nickel oxide. In one case with only 8.5% conversion to phenol ture was raised to 400 only 3.1% was recovered as phenol while 13.8% was dehydrated. Furthermore, these catalysts lost their activity rapidly in the course of a few hours.

- dehydration. was 6.3% and when the tempera- Our study of the conversion of cyclohexanol and cyclohexanone tophenoi has disclosed the importance'of operating under conditions that produce high conversions- Otherwise one encounters a very difiicult problem of recovering the phenol which is produced, This problem arises from the fact that phenol forms high boiling' binary mixtures both with cyclohexanol and with cyclohexanone. These binaries are difiicult to separate from oneanother and furthermore under such high temperature conditions cat-., I alysts that haveheretofore been disclosedjnot only lose their activity rapidlybut promote ex yiel It is an. object of this invention to overcome the disadvantages of the prior art and to provide" a new and improved process for the production I of phenol by catalytic dehydrogenation.

It is a further object to providean improved process for the catalytic dehydrogenation oi'cyclohexanol'or cyclohexanone-or their mixtures to phenoLfOtherobjects and adyantagesf ofthis invention will be apparent from the 'following specification.

According to this invention, cyclohexanolor cyclohexanone or both may be dehydrogenated to phenol with conversions approaching those'ot equilibriumlby passing these substances in vapor state over an improved dehydrogena'tiori catalyst at an elevated temperature.

The resulting con version or fraction of ketone or alcohol conthe unreacted cyclohexanol'and cyclohexanone are diflicult to separate from these binaries. In-' asmuch as the phenol-cyclohexanone binary con- V tains 29% cyclohexanone'and 7.1% phenol-by i verted to phenol may be from.80-%. 7

Our investigations show that excellent results may be obtained by passing cyclohexanol and/or cyclohexanone' over a catalyst comprising mane:

ganeseand chromium, in the form, for example, oi' manganese chromite, either unpromoted orf promoted with other constituenta'f Althou gh" cessive dehydration with consequent .loss' 01' gree of success if upwardsto manganese and chromium may be used advantageously in the form of fused. mixtures of their metals or in some form of oxidation, it is preferred to utilize them in the form of what is commonlyreferred toin the artas manganese chromite, i, e., a, mixture of manganese and chromium obtained as described in Zeitschrift fur anorg. Chemie, volume 44, page 453 (1906) and volume '76, page 30, (1912), or as prepared according to the general disclosure of ,Lazie'r U. S. 1,829,046. v

We have found further that catalysts of this type are definitely improved by the addition of small amounts of alkaline earth and alkali metal compounds as, for example, potassium carbonate. Three to five per cent by weight of the alkaline earth or alkali metal compound is sufficient to produce a real improvement in the catalytic action. Where, hereinafter as well as in the claims, we refer to alkali it is meant to include alkaline earth metals and alkali metals as such or in the form of their compounds such as oxides, salts and the like. We have also observed that catalysts such as copper and nickel, which we have already stated tend to favor undesired side reactions, are substantially improved by the addition of alkali. Our results also, show that copper, may be advantageously added to manganese chromite without producing any excessive dehydration; To"

such a copper-manganese-chromium catalyst the addition of an alkali has also been found. ad-

vantageous.

, By means of such catalysts as herein described, the conversion of cyclohexanol and/or cyclohexanone to phenol may be so high that the amount of phenol produced over that which ordinarily forms binary mixtures with cyclohexanone andjcyclohexanol is readily separated and 're-.

tillation; The unreacted cyclohexanone or cyclohexanol or both may be returned for further dehydrogenation along with the phenol associated therewith injthe form of binary'mixtures. It" shouldbe understood, however, that the use of these catalysts need not necessarily be limited to those conditions which produce phenol in excess of the requirements for binary formation as above described- Where the binaries canbe used as such or where methods for their separation are available, lower conversions and accordingly lower temperatures can be advantageouslyemployed when using the catalysts disther' feature of this .invention, that the un-- favorable side reactions can be substantially suppressed if there is present in the reaction mixture relatively small amounts of water. For example, we havefound that the presence of 05-10% (by weight) of water in the feed ofraw material has been highly effective in' inhibiting side reactions such as dehydration. Accordingly catalysts heretofore disclosed may be employed with some demoved'from' the reaction product by simple disof water is added during the dehydrogenation. Although as a rule water is not required for the type of catalysts utilized in this invention, there may be operating conditions that warrent the use of water with such catalysts... r

We have found that reduced partial pressure of reactants may be employed to favor the dehydrogenation reaction. Such reduced pressures may be established by the use of vacuum equipment or'byi means of a diluent gas such as nitrogen or vaporized benzene. However, at relatively high temperatures operation at atmospheric pressure or even higher is quite satisfactory, particularly at temperatures above 425.

Although not limiting the invention the following examples will serve to indicate how this invention may be practiced.

Example I A mixture consisting of 940 g. cyclohexanone and 60 g. water was heated to vaporization and passed at a space velocity of 250 over an alkali promoted manganese chromite catalyst in a vessel which was maintained at 525 (3.. By space velocity is meant the volume of as (calculated under standard conditions) per volume of catalyst per'hour. This quantity of cyclohexanone and water was passed during a period'fof 3 hours, at the expiration of'which time 86% of the ketone was converted to phenol and 12% was unreacted. The resulting product is distilled at a temperature of about and under 50 mm. of pressure to givea distillate containing 722 grams of phenol, 113 grams of cyclohexanone and 20 grams of high-boiling residue; -The resultant mixture is separated by further distillation to remove the pure phenol. V i Example II In a manner similar to that described in Example I, cyclohexanol containing 6.3% water by weight was vaporized and passed over a Cu-Mn chromite catalyst at total inlet spacevelocity of I 137. Total pressure was one atmosphere and the temperature was 425 :C. 77% of the cyclohexanol was converted to phenol, 15% to cyclohexanone,

and 8% toby-products (benzene, cyclohexene and tar). z

- Example III In a manner similar to that of Examples I and II, a mixture of 98 g. cyclohexanone and '18 g.

benzene was'vaporized and passed over a potasslum carbonate promoted copper manganese chromite catalyst at a space velocity of 250 and at 425 C., under one-atmosphere total pressure.

62% of the ketone' was converted to phenol, 26%

was unreacted and 12% went to side reactions.

If, after operation of this invention, a resinous deposit or layer appears upon the surface of the catalyst, it may beremoved by oxidizing the catalyst with oxygen or air at an elevated temperature of, say, 350 to 500 C., following which it may be reduced before further use if desired.

Various changes may be made in the, details of the present invention without-departing therefrom or sacrificing any'of the advantages thereof.

' ,We claim: a

1. The process for the production of phenol which comprises passing a material selected from the group consisting of cyclohexanoland cyclohexanone over a copper-manganese chromite dehydrogenation catalyst at a temperature within the range of 350 to 600" C. and removing phenol from the resultant product.

2. The process for the production of phenol which comprises passing a material selected from the group consisting of cyclohexanol and cyclohexanone over a copper-manganese chromite dehydrogenation catalyst at a temperature within the range of 425 to 550 C. and removing phenol from the resultant product. Y I

3. A process for the production of phenol which comprises passing a substance selected from the group consisting or cyclohexanol and cyclohex-- anone, over a manganese chromite dehydrogenation catalyst at a temperature within the range 350 to 600 C. and at a pressure within the range 200 mm. to atmospheres, and removing phenol from the resultant product.

4. A process for the production of phenol which comprises heating a substance selected from the group consisting oi cyclohexanol and cyclohexanone at a temperature within the range offrom reaction being carried on in the presence oi from reaction being carried on in the presence of from 350 to 600 0., in the presence oi a catalytic body 1 selected from the group consisting of manganese chromite and copper-manganese chromitev 5. A process for the production of phenol which comprises heating a substanceselected from the group consisting of cyclohexanol and cyclohexanone at a temperature within the range of from.

350 to 600 C., in the presence of manganese chromite.

6. A process for the production of phenol which comprises heating a substance selected from the group consisting of cyclohexanol and cyclohexanone at a temperature within the range oi. from 350 to 600 0., in the presence of copper-manganese chromite.

7. A process for the production of phenol which comprises heating a substance selected from the group consisting of cyclohexanol and cyclohexanone at a temperature within the range 01' from 350 to 600 C., in the presence of manganese chromite, together with a promoter selected from the group consisting of alkali metals and alkaline earth metals and their salts.

8. A process for the production of phenol which comprises heating a substance selected from the group consisting of cyclohexanol' and cyclohexanone at a temperature within the range of from 350 to 600 C., in the presence of copper-manganese chromite, together with a promoter sebased upon the weight of lected from the group consisting of alkali metals" and alkaline earth metals and their salts.

9. A process for the production of phenol which comprises heating a substance selected from the group consisting of cyclohexanol and cyclohexanone at a temperature within the range of from selected from the group consisting oi manganese chromite and copper-manganese chromite, the

' reaction being carried on I .0.5 to 10% of water, based upon the weight of 350 to 600 C., in the presence of a catalytic body 0.5'to 10% of water, reactant.

11. A process for the which comprises heating from the group consisting of cyclohexanol and cyclohexanone at a temperature within the range oi from 350 to 600 C., in the presence of manganese chromite, the reaction being carried on in the presence of from 0.5 to 10% of water, based upon the weight of the reactant. a

12. A process for the production of phenol which comprises heating a substance selected from the group consisting of cyclohexanol and production of phenol cyclohexanone at a temperature within the range of from 350 to 600 C., in the presenceoi' coppermanganese chromite, the reaction being carried on in the presence of from 0.5 to 10% of water,

the reactant.

13. A process for the production of phenol which comprises heating a substance selected from the group consisting of cycl'ohexanol and cyclohexanone at a temperature within the range of from 350 to 600 C., in the presence of man ganese chromite, together with a promoter selected'irom the group consisting of alkali metals and alkaline earth metals and their salts, the reaction being carried 0.5 to 10% of the reactant.

14. A process for the production of phenol which comprises heating'a substance selected from the-group consisting of cyclohexanol and cyclohexanone at a temperature within the range of from 350 to 600 C., in the presence of coppermanganese chromite, together with a promoter selected from thegroup consisting of alkali metals and alkaline earth metals and their salts, the

water, based upon the weight of the reactant. 1 v

EDWARD P. BARTLETT.

based upon the weight of the a substance selected on in the presenceoffrom in the presence of from. 

